A new wave of consolidation, with insurance companies doing more of the bidding, could be in the making as Wall Street prepares for a flurry of initial public offerings by some of the nation's biggest insurers.

On Thursday, Boston-based John Hancock Mutual Life Insurance Co. is expected to fetch between $1.5 billion and $1.8 billion in its first public stock offering. The company has said repeatedly that it hopes to use proceeds of the offering as currency for acquisitions and for employee incentives.

John Hancock is far from alone. This spring Metropolitan Mutual Life Insurance Co. plans to launch its own offering, in what could become the biggest IPO to date, with an estimated value of more than $5 billion. Prudential Insurance Company of America is in the early planning stages of an IPO, one that could take place this year.

Though those billions of dollars would bring considerable heft to the insurers, few believe those companies will be in any position to pick off the nation's largest banks, given the banks' far bigger capital base and generally higher profitability and stock multiples.

Analysts said they expected John Hancock's acquisition plans to take shape in one of two main ways, either with the purchase of competitors in the life business or with deals for small to mid-sized banks that would also bring strong asset management operations to the mix.

Even given those limitations, observers said blockbusters deals were still conceivable once the IPOs were completed. Some early speculative talk on Wall Street has paired MetLife with Fidelity Investments, Prudential with Charles Schwab & Co., and John Hancock with State Street Corp.

"These are the types of deals they should be looking at," said David Kaytes, a consultant specializing in insurance at New York-based Novation Associates. "You can envision all kinds of plays that wouldn't have been possible before."

Other insurance companies, taking their cues from elsewhere in the financial services industry, have focused on internal efficiency. Conseco Inc., one of the most acquisitive companies in recent years, has pledged to slow down a bit and make its existing operations more efficient.

Despite - or perhaps because of - their stronger returns, banks are not expected to rush out on an acquisition binge for insurers anytime soon. Insurance as a business typically earns returns on equity about half that of the typical bank. "There are few banks that, given current pressure on earnings, are going to want to absorb a company like that," Mr. Kaytes said.

The three IPOs would leave New York Life Insurance Co., Guardian Life Insurance Co., Principal Financial Group, and Northwestern Mutual Life Ins. Co. as the mutual holdouts among the largest U.S. life insurers. Stock offerings have gained favor with insurance companies as they try to free up hidden capital to expand into new markets and develop new products and distribution avenues.

For converting mutual companies, the adjustment will also take time. Owned by their policyholders, the mutuals are viewed as "not accountable to anyone," said Colin Devine, an analyst at Salomon Smith Barney.

For example, the companies are being forced to take care of their accounting housekeeping more aggressively. John Hancock said Sunday that it would take a $134 million after-tax hit to fourth-quarter earnings to cover losses from a pool of workers' compensation policies.

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